Image processing device

ABSTRACT

An image processing device is provided with a scanning means which performs subscanning by a pitch corresponding to a width covering a number of pixels less than the number of detectable pixels by a one dimensional image sensor by two or more pixels so as to overlap two or more line pixels. An edge emphasizing means performs an edge emphasis processing for the pixels from the second pixel to the second last pixel according to the image data obtained in response to the scanning by the scanning means.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image processing device and, morespecifically, relates to an improvement in an emphasis processing in adigital type copying machine, an image scanner and the like whenperforming an edge emphasis processing for read data.

2. Background Art

In an image scanner and the like, an original image is developed intopixels, the gray levels of the respective pixels are read as gray levelsignals and the read signals relating to the image are outputted such asto a laser printer through a pseudo intermediate gradient processing ofbinary value data. In such case or in a case when an image is inputtedand outputted in a digital type copying machine an edge emphasisprocessing or a nonuniformity correction processing for input image datais performed in order to obtain a high quality image. The pseudointermediate gradient processing was invented by the present inventorand was already patented as U.S. Pat. No. 5,307,425.

In an edge emphasis processing, a gray level of a certain pixel, whichis obtained via individual light receiving parts or light receivingelements arranged correspondingly to respective pixels, is detected as agray level signal (normally an analog value) and a detected value (whichis normally a digital value converted from the above analog value) ofthe noted pixel determined in accordance with the detected value iscorrected by detected values of the pixels surrounding the noted pixel.For this purpose, it is necessary to refer to detected values of thepixels on scanning lines immediately before and after the currentscanning line. Accordingly, a memory is necessary which stores thesedetected values (digital values) of the respective pixels as pixel data.

On the other hand, in these days a plurality of main scanning lines aresimultaneously scanned by a single main scanning operation. In suchinstance, the pixel data (detected values of the respective pixels) onthe scanning lines immediately before and after the current scanningline are normally stored simultaneously in the memory. However, for theedge emphasis of the last line among the plurality of main scanninglines, pixel data of the first line obtained in the subsequent mainscanning operation is necessary, therefore the edge emphasis processingfor the last line is required to wait until the pixel data of thesubsequent first line is obtained. Further, for the edge emphasis of thefirst line in the subsequent main scanning operation the pixel data ofthe last line in the immediately before main scanning operation isnecessitated, therefore the pixel data of the last line have to bepreserved. For this reason, in such a scanner that reads image data byscanning a plurality of main scanning lines simultaneously, a memory isnecessary which stores detected values of the pixels covering the lastone line and the subsequent first one line.

FIG. 5 and FIGS. 6(a) and 6(b) are diagrams for explaining relationshipsbetween scanning operation and edge emphasis processing when a pluralityof main scanning lines are simultaneously scanned by a single scanningoperation.

As shown in FIG. 5, a scanner is provided with a CCD sensor 11 for 128pixels (with regard to pixels see FIG. 6(a)) located in verticaldirection (in the subscanning direction). Through a single scanningoperation a main scanning covering 128 lines is simultaneously performedwith a vertical width covering 128 pixels. After one main scanningoperation has completed, the scanner moves in vertical direction (in thesubscanning direction) by the width covering 128 pixels for thesubsequent main scanning operation within return time in the retraceinterval (see FIG. 5).

In an edge emphasis processing, for example as shown in FIG. 6(b), anedge emphasized value X is calculated with reference to the detectedvalues a, b, c and d of the surrounding 4 pixels and according to anequation, for example, X=x-α(a+b+c+d-4x), wherein α is a predeterminedcoefficient.

Therefore, for the pixels on the joint portions in the subscannings thedetected data of pixels obtained in the subsequent main scanningoperation or in the immediately before main scanning operation arenecessitated.

In FIG. 6(a), the blocks indicated by numerals 1 are first pixels andthe blocks indicated by numerals 128 are last pixels for the CCD sensor11, and for the above indicated reason as a memory for storing thedetected values of these pixels, a line memory covering two line pixelsalong the main scanning direction (pixels on a main scanning line aredefined as one line pixels) is incorporated in a device. Accordingly, atthe moment when the detected values (pixel data) of the respectivepixels are inputted which are obtained from the CCD sensor 11 at thesubsequent scanning point (respective measurement points of the CCDsensor 11 along the main scanning direction), the one line before pixelcorresponding to the pixel on the scanning point immediately before thesubsequent scanning point (the detected value of the pixel is stored inthe memory) is noted and the edge emphasis processing is performed forthe noted pixel while referring to the detected values of the previoustwo line pixels stored in the line memory.

Namely, in order to edge emphasize the last line pixels and the firstline pixels in the subsequent scanning operation, data on the scanninglines before and after the concerned line are necessitated. Therefore,data covering one scanning line have to be stored in the memory for therespective last and first line pixels, such that a line memory having astorage capacity covering at least two scanning line data has to beprovided. The longer the width in the main scanning direction, thelarger the capacity of the line memory. Further, the line memory has tobe provided separate from an image memory, therefore the control thereofis also performed independent from that for the image memory.Accordingly, a separate control circuit therefor is necessitated.

In this type of scanners, the line memory is assembled into the CCDsensor so as to keep a required performance and to meet a required sizereduction. However, when assembling the line memory, because of alimited room in the sensor portion there arise problems that the circuitassembling is difficult and the working therefor is lower. Further, dueto such assembling the scanner itself becomes expensive as well as thesize reduction thereof becomes difficult.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an image processingdevice which permits an edge emphasis processing without using one linememory for an edge emphasis.

The image processing device according to the present invention, whichachieves the above object and in which the arranging direction of lightreceiving portions or light receiving elements in an image sensorarranged in correspondence with pixels to be detected is to correspondto the subscanning direction, through the main scanning by the imagesensor in the main scanning direction gray level signals of therespective pixels are obtained from the image sensor and an edgeemphasis processing is performed in response to the values of the graylevel signals. A scanning means performs the subscanning by a pitchcorresponding to a width covering pixels of which number is less thanthe number of the pixels in the arranging direction covered by the lightreceiving portions or the light receiving elements by equal to or morethan two pixels. An edge emphasizing means performs an edge emphasisprocessing for the second pixels to the second last pixels defined bythe arranging direction based on the gray level signals obtained inresponse to the scanning in the main scanning direction are provided,and after completing the main scanning the subscanning is performed bythe scanning means.

When equal to or more than two pixels in the subscanning direction areoverlappingly scanned as explained above, the data of equal to or morethan the last two pixels in the subscanning direction are obtained inthe subsequent scanning operation.

For example, an overlapping scan covering two line pixels is performedand the edge emphasis processing is performed from the second linepixels in the subsequent main scanning operation, the edge emphasisprocessing corresponds to that for the last line pixels in theimmediately before main scanning operation.

Accordingly, the edge emphasis procesing for the last line pixels in theimmediately before main scanning operation is obtained in the edgeemphasis processing in the subsequent main scanning operation. As aresult, the line memory specifically provided in the CCD portion for theedge emphasis for the joint portion pixels in subscanning direction canbe eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of one embodiment of the image processingdevice according to the present invention;

FIG. 2 is a diagram for explaining a relationship between edge emphasisprocessing and pixels in the embodiment;

FIG. 3 is a diagram for explaining a scanning operation in theembodiment;

FIG. 4 is a diagram for explaining a relationship between overlappingprocessing of two line pixels and edge emphasis processing thereof inthe embodiment;

FIG. 5 is a diagram for explaining a scanning operation when a pluralityof main scanning lines covered by a sensor are simultaneously scanned;and

FIG. 6(a) and FIG. 6(b) are diagrams for explaining a general edgeemphasis processing, wherein FIG. 6(a) is a diagram for explaining ageneral scanning operation and FIG. 6(b) is a diagram for explaining anexample of edge emphasis processings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, numeral 10 is an image processing device in which an originalimage 1 is read via a detection unit 2 and gray levels of respectivepixels of the original image 1 arranged in the subscanning direction aredetected in a form of gray level signals via one dimensional CCD imagesensor (hereinafter called as CCD sensor) 2a. These detected signals forthe first pixels to the last pixels are successively and serially sentout from the CCD sensor 2a to an analog signal processing unit 3. TheCCD sensor 2a is equivalent to the CCD sensor 11 as shown in FIG. 5 andin which light receiving portions or light receiving elements covering128 pixels in the vertical direction (in the subscanning direction) arearranged. Numeral 2b is a lens provided in the detection unit 2 andwhich causes to focus the image of the original image 1 onto the CCDsensor 2a.

The analog signal processing unit 3 is constituted by an amplifier (AMP)3a, an A/D converter circuit (A/D) 3b and a CCD control circuit (notshown), reads serially the detection signals (gray level signals) of the128 pixels from the CCD sensor 2a in response to sampling signals andcontrol signals from a control unit 5, amplifies the same in theamplifier 3a and thereafter sends out the amplified signals to the A/D3b. The A/D 3b converts the levels of the detected signals of therespective pixels into digital data of 256 gradations in 8 bits inresponse to the sampling signals from the control unit 5 and sends outthe same to an input data correcting unit 4.

The input data correcting unit 4 is constituted by a shading correctioncircuit 4a, a buffer memory 4b and a first line pixels and last linepixels excluding edge emphasizing circuit 4c and is also controlled viasignals from the control unit 5. The digital data inputted from theanalog signal processing unit 3 are at first inputted into the shadingcorrection circuit 4a in the input data correcting unit 4, wherein aprocessing is performed in accordance with a predetermined referencewhich is read in advance to thereby correct the non-uniformity thereof.The non-uniformity corrected data are sent out from the shadingcorrection circuit 4a to the buffer memory 4b to store therein and arefurther sent out to the first line pixels and last line pixels excludingedge emphasizing circuit 4c. The shading correction used in the presentembodiment is one generally known, therefore the explanation thereof isomitted.

The buffer memory 4b stores the non-uniformity corrected data coveringtwo column scanning points (2 measurement points) in the main scanningdirection, namely the first pixel--the 128th pixel covered by the CCDsensor 11 contained in two lines in vertical direction (256 pixels intotal). In this instance, the data at one column scanning points in themain scanning direction contain those of 128 pixels corresponding to thewidth of the subscanning, therefore the data stored in the buffer memory4b amounts 128 pixel×2 pieces.

The first line pixels and last line pixels excluding edge emphasizingcircuit 4c excludes the edge emphasis processing for the data of thefirst pixels 1 (data of the first line pixels) and the data of thepixels 128 (data of the last 128th line pixels), starts the edgeemphasis processing for the data of the second line pixels and ends theedge emphasis processing at the 127th pixels. Namely, although the sameprocessing as in the conventional edge emphasis processing is performed,the processing object is limited to the pixels 2 --pixels 127 and thefirst pixels and the last pixels are excluded from the processing. Suchoperation is realized, for example, when setting pixel numbers at acounter which designates the pixel numbers to be processed, the notedpixel number 2 is first set instead of setting noted pixel number 1 andthe ending pixel number 127 is lastly set instead of setting endingpixel number 128.

When a plurality of main scanning lines are simultaneously scanned, theedge emphasis processing is possible as shown in FIG. 6(b) if pixel data(detected values of respective pixels) covering surrounding 4 pointscontained in three lines including before and after thereof in the mainscanning direction (continuous three line pixels in the main scanningdirection) are obtained. Therefore, in the present embodiment the edgeemphasis processing is performed by making use of the digital value dataafter the shading correction of the 2 vertical line pixels stored in thebuffer memory 4b and the pixel data currently inputted from the analogsignal processing unit 3 (the detected values after shading correction).

For simplifying the explanation, at first the explanation is startedspecifically under a condition that all of the data for the edgeemphasis processing are prepared.

It is assumed that the buffer memory 4b stores the pixel data of 128pieces detected at the first scanning points by the CCD sensor 11 duringthe main scanning as well as the pixel data of 128 piece detected at thesubsequent scanning points. Then, it is further assumed that the CCDsensor 2a moves up to the third scanning points. At the moment when thefirst line pixels and last line pixels excluding edge emphasis circuit4c has received data covering 128 pixels at the third scanning points,more precisely at the timing when the CCD sensor 2a has received thedata of the second pixel at the third scanning point, the up and downand right and left surrounding data with respect to the detected value xof the second pixel at the second scanning point immediately before byone scanning point, in that the surrounding data a, b, c and d as shownin FIG. 6(b), are prepared. Namely, at this moment the data a, b, and camong these surounding data are stored in the buffer memory 4b and thedata of the second line pixel at the third scanning point has beenreceived as data d.

Under this condition, while noting the second line pixel at the secondscanning point which is immediately before the current third scanningpoints, the first line pixels and last line pixels excluding edgeemphasis processing circuit 4c starts the edge emphasis processing forthe noted pixels with reference to the data of 128 pixels×2 pieces(respective data a, b, and c among these data) stored in the buffermemory 4d. The manner of the processing which is explained previously isas follows, in that a value X of the noted second pixel is calculatedthrough an arithmetic processing of, for example, X=x-α(a+b+c+d-4x)based on the detected value x and the calculated value X is sent out toan image processing unit 6 as the edge emphasized value of the secondline pixel.

At the moment when the above edge emphasis processing is completed thesurrounding data b at the scanning point immediately before the edgeemphasized pixel as shown in FIG. 6(b) becomes unnecessary, thereforethe data x at the second scanning point in the buffer memory 4b isstored at the position of the data b at the first scanning point.Further, the data x serves as a reference pixel equivalent to the pixelhaving value a during the subsequent edge emphasis processing for thethird pixel, therefore the data x is preserved as it is and is used forthe subsequent edge emphasis processing of the third pixel.

The data at the third scanning points which are currently being receivedfrom the CCD sensor 2a are temporarily stored at a temporary register(not shown) in the first line pixels and last line pixels excluding edgeemphasizing circuit 4c. Then, at the timing when the data of the thirdpixel at the third scanning point is received from the CCD sensor 2a,the third pixel at the second scanning point is noted and the sameprocessing as explained above is repeated for the newly noted pixel. Atthe moment when the edge emphasis processing of the pixel at the thirdis completed the data x is unnecessary, therefore the data of the secondpixel at the third scanning point received immediately before from theCCD sensor 2a and stored in the temporary register is stored at theposition occupied by the data x. Thereby, the data of third pixel at thethird scanning point which is currently being received from the CCDsensor 2a is stored at the temporary register.

Every time when pixel data at the third scanning points are received,the edge emphasis processing on the data from below the third pixel tothe 127th pixel at second scanning points, the data updating of thesecond scanning points and the temporary data storage of the thirdscanning point are successively performed.

In the above case, the edge emphasis processing is performed from thesecond scanning pants. When performing the edge emphasis processing onthe pixels at the first scanning points, at the moment when the secondpixel data at the second scanning point is received from the CCD sensor2a, the pixel of the second line at the first scanning point is notedwhich is immediately before the second pixel received of the data. Forthe pixels at the first scanning points the edge emphasis processing isstarted from the second pixel at the first scanning point with referenceto the data of 128 pixels×1 pieces stored at the buffer memory 4b.

In this instance, among respective surrounding pixel data required forthe edge emphasis processing data corresponding to the surrounding datab as shown in FIG. 6(b) is lacking which is immediately before the firstscanning points, therefore, using predetermined data values set for thedata immediately before the first scanning points the edge emphasisprocessing is performed. Further, for the sake of convenience the edgeemphasis processing for the pixels at the second scanning points is atfirst explained, however in actual practice the edge emphasis processingis performed first for the pixels at the first scanning points.

Such actual processing is explained specifically with reference to FIG.2 wherein the vertical block indicated by * represents positions usingpredetermined data, the vertical block indicated by (1) represents thefirst scanning points during the first scanning and the vertical blockindicated by (2) represents the subsequent second scanning points. Inthe buffer memory 4b the data of 128 pixels indicated in the verticalblock (1) are stored and the first line pixels and last line pixelsexcluding edge emphasizing circuit 4c receives successively the data of128 pixels from pixel 1 to pixel 128 in the vertical block (2). At themoment when the data of the second pixel at the vertical block (2) isreceived, the data of the second pixel at the vertical block (1) isassumed as x and then the edge emphasis processing for the data x isperformed according to the above mentioned equation using a, b, c, d andx, and such processing is ended at the pixel 127. Thereafter, at themoment when the data of pixel 2 in the vertical block (3) is received,the relationship between a, b, c, d and x is shifted rightward and theobject x of the edge emphasis processing is moved to the second pixel inthe vertical block (2). Since the data in the vertical blocks (1) and(2) are already stored in the buffer memory 4b, the edge emphasisprocessing for from the second pixel to the 127th pixel in the verticalblock (2) which now constitute the objects for the edge emphasisprocessing is performed by using the stored pixel data in the verticalblocks (1) and (2) and the pixel data in the vertical block (3) nowreceiving with reference to the relationship as shown in FIG. 6(b).Further, after the last measurement points at which the main scanningoperation is ended, no input data are received, therefore in the likemanner as for the 128 pixels in the vertical block (1), a vertical blockindicated by * containing predetermined data values is added after theblock for the last measurement points and the edge emphasis processingfor the pixels at the last measurement points is performed by making useof the predetermined data values in the added vertical block.

In the manner as explained above, the data contents of 128 pixels×2pieces stored in the buffer memory 4b is successively updated and theedge emphasis processing is successively performed for the pixels fromthe second pixel to the 127th pixel with reference to these updateddata.

The respective edge emphasized data are successively sent out to theimage processing unit 6 wherein a binary coding processing such as apseudo intermediate gradient processing is performed and the processeddata are sent out to a print output unit 7.

Numeral 8 is a scanner mechanism unit controlled by the control unit 5and constitutes a scanner together with the detection unit 2. The pitchin the subscanning direction of the scanner mechanical unit 8 is setsmaller by a width corresponding to two pixels than the number of pixelsarranged in the subscanning direction and covered by the CCD sensor 11with the respect to the detection unit 2 as shown in FIG. 3 and FIG. 4,namely a pitch corresponding to a width of 126 pixels is set for thescanner mechanism unit 8 and an overlapping subscanning covering twoline pixels is performed.

The control unit 5 is constituted by a MPU 5a and a memory 5b, and isprovided with a two line pixels overlapping scanning program 5c whichperforms an overlapping scanning of two line pixels.

In the two pixels overlapping scanning program 5c the subscanning widthis set to cover 126 pixels in contrast to the conventional subscanningwidth covering 128 pixels, however other than the difference in thesubscanning width the two pixels overlapping scanning program 5c issubstantially the same as the conventional scanning program. Namely,when returning after completing the last one line in one main scanningoperation shown in FIG. 5, the returning position of the retrace line issimply shifted upward by a distance corresponding to two pixels, therebythe first two pixels for the subsequent scanning by the CCD sensor 11are overlapped.

Numeral 9 is an exposure control unit which is constituted by a lightsource 9a and light quantity control unit 9b which controls the quantityof light of the light source 9a.

FIGS. 3 and 4 are diagrams for explaining the edge emphasis processingwhen the two line pixels overlapping scanning is performed by thescanner mechanism 8.

Numeral 12 indicates a first main scanning operation and numeral 13indicates the subsequent main scanning operation. In this subsequentmain scanning operation after the first main scanning operation two linepixels components are overlappingly scanned, therefore the last twopixels 127 and 128 in the first main scanning operation corresponds tothe first and second pixels 1 and 2 in the subsequent main scanningoperation and the last pixels 128 in the previous main scanningoperation 12 are taken up as the object of the edge emphasis processingfor the second pixels 2 in the subsequent main scanning operation.Accordingly, all of the pixels except for the first line pixels in thefirst main scanning are taken up as the object of the edge emphasisprocessing and no line memories for the joint processing and for thejoint itself are necessitated.

In the embodiment of the present invention, two pixels are overlappinglyscanned in the subscanning direction, it is of cource possible to beoverlappingly scanned of equal to or more than three pixels depending onthe scanning in the subscanning accuracy in the subscanning direction.Further, depending on arithmetic operation used for the edge emphasisprocessing it is also possible to make use of further more surroundingdata while performing the overlapping scanning of equal to or more thanthree pixels.

In the above, the one dimensional image sensor is explained, however theimage sensor is not limited thereto, in that with a two dimensionalimage sensor detection signals corresponding to respective pixels can betaken out one-dimensionally along the subscanning direction.

I claim:
 1. An image processing device in which the arranging directionof light receiving portions or light receiving elements in an imagesensor arranged in correspondence with pixels to be detected isdetermined to correspond to the subscanning direction, through the mainscanning by said image sensor in the main scanning direction, gray levelsignals of the respective pixels are obtained from said image sensor andan edge emphasis processing is performed in response to the values ofthe gray level signals obtained, the image processing devicecomprising:a scanning means which performs the subscanning by a pitchcorresponding to a width covering line pixels of which number is lessthan the number of the line pixels covered by either the light receivingportions or light receiving elements in said image sensor in thearranging direction by two or more pixels; and an edge emphasizing meanswhich has a buffer memory to store therein data corresponding to thegray level signals from the image sensor obtained in said subscanningdirection and performs an edge emphasis processing from the second pixelto the second to last pixel excluding a first pixel and a last pixeldefined by the arranging direction based on data from said buffer memoryin response to the scanning in the main scanning direction, and whereinafter completing the main scanning the subscanning is performed by saidscanning means.
 2. An image processing device according to claim 1,wherein said edge emphasizing means performs the edge emphasisprocessing for the respective pixels in the subscanning direction at thefirst scanning point and the last scanning point in the main scanning bymaking use of predetermined set data values.
 3. An image processingdevice according to claim 1, further comprising an A/D convertercircuit, a shading correction circuit and a buffer memory, wherein saidimage sensor is a one dimensional CCD sensor, the gray level signals areconverted into digital values by said A/D converter circuit, theconverted digital values are shading-corrected by said shadingcorrection circuit and stored in said buffer memory, with regard to thegray level signals of the respective pixels arranged in the subscanningdirection each shading corrected digital value of the pixels at thescanning point which locates prior to the current scanning point in themain scanning by two pixels and each shading corrected digital value ofthe pixels at the scanning point which locates prior to the currentscanning point in the main scanning by one pixel are stored in saidbuffer memory, and said edge emphasizing means performs the edgeemphasis processing upon receipt of the shading-corrected digital valueof a certain pixel at the current scanning point from said shadingcorrection circuit and with reference to the digital values stored insaid buffer memory for the pixel prior to the certain pixel in the mainscanning by one pixel.
 4. An image processing device according to claim3, wherein said CCD sensor is one which outputs successively andserially the gray level signals for the respective pixels from the firstpixel to the last pixel, said A/D converter circuit is one whichsuccessively converts the gray level signals, and at the moment whenreceived of the shading corrected digital value of the certain pixel atthe current scanning point said edge emphasizing means performs anarithmetic operation for the edge emphasis for the pixel prior to thecertain pixel in the main scanning by one pixel and with reference tothe shading corrected digital values for the surrounding pixelstherearound.
 5. An image processing device according to claim 4, whereinsaid edge emphasizing means is an edge emphasizing circuit whichedge-emphasizes the respective pixels excluding the first pixel and thelast pixel which are detected by said CCD sensor.
 6. An image processingdevice according to claim 5, wherein the number of pixels arranged inthe subscanning direction which are to be scanned by said onedimensional CCD sensor is 128 pixels and said edge emphasizing meansperforms the edge emphasis processing for the pixels from the secondpixel to the 127th pixel.